The annexed engravings are views of an evaporator for marine steam boilers, to supply any deficit of pure water by the surface condenser of James. M. Miller, of this city. The condenser was illustrated and described on water is introduced inside by forcing it by a pump through the pipe, Z, wkich can be washed out, when saturated, by the pipe, Y. This apparatus is placed nearer to the boiler than the heater, represented on the page referred to above. K K is the pipe which connects the exhaust pipe of the steam engine with the condenser. The vessel being filled with salt water, the steam of the exhaust passes up into the pipes, C C, figure 2, from thpipe, K, kik ig opoa ingiflw to allow this. Two of the tubes are represented in WH. Allowing the salt water to be cold, when the steam is first let in, condensation of the steam will take place for a short time, but it will flow onwards to the condenser. When the salt water is heated to steam heat, moderate evaporation will take place, and the vapor will pass up and then down the pipe, V, into the condenser; W is a cock to open or close communication with the vaporization chamber; S S are flanges to support the apparatus and bolt it on a suitable bed-plate; X X are side flanges which perform the office of braces ; P is the bottom plate. All the outside parts are of cast-iron, and are made strong and durable. Water gives off some vapor, at a lower temperature than 212 as can be noticed in any boiler or during solar influence. A small apparatus of this kind, used perhaps once or twice on a voyage across the Atlantic, it is believed will be sufficient to make up any slight loss of condensed steam, to be used